Technical Field
[0001] The present invention relates to a tire in which a tire frame member is formed using
a resin material.
Background Art
[0002] Hitherto, tires are known that are formed from rubber, organic fiber material, and
steel members. Recently, there is demand for tire frame members to be made from thermoplastic
polymers, such as thermoplastic elastomers (TPE) and thermoplastic resins in order
to achieve weight reductions and easy recycling. For example, Japanese Patent Application
Laid-Open (
JP-A) No. 3-143701 describes forming a tire frame member in which a bead core is covered in a thermoplastic
elastomer, disposing a reinforcing layer on the outer circumference of the tire frame
member, further disposing a tread member on the outer circumference thereof, and performing
vulcanization bonding. Attention is drawn to the disclosures of
EP2987650 and
EP2960077, which form part of the state of the art under Article 54(3) EPC, and to the disclosure
of
EP2399761, on which the preamble of claim 1 is based.
SUMMARY OF INVENTION
Technical Problem
[0003] In a tire axial direction cross-section of an ordinary tire, a reinforcing layer
and the tread face of the tread have curvatures that curve about different centers
on the tire radial direction inside, so as to protrude toward the tire radial direction
outside. Accordingly, the tread and the reinforcing layer deform so that their curvatures
decrease and they flatten out when the tread contacts the ground (under load from
the road surface). The deformation of the reinforcing layer leads to an increase in
the rolling resistance.
[0004] In the conventional example given above, in tire axial direction cross-section, the
outer circumferential surface of the crown portion of the tire frame member is formed
so as to be flat along the tire axial direction, and a reinforcing layer is disposed
along this outer circumferential surface. Thus, a suppression of deformation of the
reinforcing layer under load is conceivable compared to ordinary tires.
[0005] However, in the example given above, the tread face of the tread has a curvature
similar to that of an ordinary tire, and the tread face of the tread deforms so as
to flatten along the road surface under load. In addition, the end portions of the
reinforcing layer in the tire axial direction extend as far as shoulder portions of
the tire frame member. It is accordingly conceivably difficult to suppress deformation
of the edge portions of the reinforcing layer under load.
[0006] In consideration of the above circumstances, an object of the present invention is
to reduce rolling resistance.
Solution to Problem
[0007] A tire according to the present invention is provided as claimed in claim 1.
[0008] In this tire, the reinforcing layer is provided to the tire frame member along the
outer surface of the flat crown portion, and the end portions at the tire axial direction
outside of the reinforcing layer are positioned further to the tire axial direction
inside than the tire axial direction outside end portions of the flat crown portion.
This thereby enables deformation of the reinforcing layer under load to be suppressed
more than in cases in which the end portions of the reinforcing layer extend in the
tire axial direction up to the shoulder portions of the tire frame member. This thereby
enables rolling resistance to be reduced.
[0009] In this tire, the end regions at the outer surface of the tread are positioned further
to the tire radial direction inside than the extension line of the central region,
thereby enabling ground contact of the end regions, where the reinforcing layer is
not present in the layer below, to be suppressed. This thereby enables uneven wear
resistance performance to be improved at the end regions of the tread.
[0010] Preferably, in the tire axial direction cross-section, the end regions are formed
so as to be circular arc-shaped having a center of curvature on a tire outside.
[0011] In this tire, the end regions are formed so as to be circular arc-shaped having a
center of curvature on the tire outside, enabling ground contact of the end regions
to be further suppressed. This thereby enables uneven wear resistance performance
to be improved even more at the end regions of the tread.
[DELETED]
[0012] In this tire, due to the outer surface of the flat crown portion where the reinforcing
layer is disposed being flat, both rolling resistance and uneven wear resistance performance
can be achieved at the end regions by making D/TW fall within the above range. Advantageous
Effects of Invention
[0013] As explained above, the tire according to the present invention is able to obtain
the excellent advantageous effect of being able to reduce rolling resistance.
BRIEF DESCRIPTION OF DRAWINGS
[0014]
Fig. 1 is a cross-section illustrating a tire sectioned along the tire axial direction.
Hatching is omitted.
Fig. 2 is an enlarged cross-section illustrating a tire sectioned along the tire axial
direction.
DESCRIPTION OF EMBODIMENTS
[0015] Explanation follows regarding embodiments to implement the present invention, with
reference to the drawings. In Fig. 1, a tire 10 according to the present exemplary
embodiment includes a tire frame member 12, a reinforcing layer 14, and a tread 16.
[0016] The tire frame member 12 is configured from a resin material. The tire frame member
12 is provided with side portions 18, shoulder portions 20, and a flat crown portion
22.
[0017] The side portions 18 are respectively positioned at both sides of a tire axial direction
(arrow A direction) sides, and are connected to a pair of bead portions 24 at a tire
radial direction outside. An annular shaped bead core 26 is embedded in each of the
bead portions 24. The bead cores 26 are configured by winding a bead cord plural times
in an annular shape, or by forming a cable cord formed from plural twisted strands
into an annular-shape.
[0018] A bead cord may employ a steel cord configured by twisting together plural steel
filaments. The outer surfaces of the filaments may be plated, such as by zinc plating,
copper plating, or brass plating. A cord made from another metal may be employed as
the bead cord.
[0019] The shoulder portions 20 are connected to a tire radial direction outside end portions
of the side portions 18, and, in a tire axial direction cross-section, curve so as
to protrude toward a tire outside. The center of curvature O of the shoulder portions
20 is positioned at the inside of the tire frame member 12 in the tire axial direction
cross-section. In the present exemplary embodiment, the center of curvature O of the
shoulder portions 20 means the center of curvature of the inner surface at the shoulder
portions 20. In cases in which the outline profile of the inner surface of each of
the shoulder portions 20 is configured from plural curved lines, the center of curvature
O of the shoulder portion 20 means the center of curvature of the circular arc having
the smallest radius of curvature.
[0020] The radius of curvature RI of the inner surface of the shoulder portions 20 is, for
example, from 4.5 mm to 30 mm. The radius of curvature RO of the outer surface of
the shoulder portions 20 is, for example, from 7 mm to 32.5 mm. The center of curvature
of the outer surface may be aligned with the center of curvature O of the inner face,
or may be different therefrom.
[0021] The radius of curvature of the inner surface of the side portions 18 (not illustrated
in the drawings) is 1 to 20 times the radius of curvature RI of the inner surface
of the shoulder portions 20. The degree of curvature (curvature) of the side portions
18 is accordingly smaller than that of an ordinary tire.
[0022] The flat crown portion 22 is connected to the shoulder portions 20. The outer surface
22A of the flat crown portion 22 is formed along a tire axial direction in the tire
axial direction cross-section, and is connected to the outer surfaces of the shoulder
portions 20. In other words, the outer surface 22A of the flat crown portion 22 is
tangent to the outer surfaces of the shoulder portions 20. The meaning of flat is
not limited to completely flat profiles. The outer surface 22A of the flat crown portion
22 may have a slightly undulating shape, as long as the undulations can be ignored
in terms of their effects on deformation of the reinforcing layer 14 under load. When
warping and shrinking of the resin material during molding of the tire frame member
is considered, the tolerance between the highest value and the lowest value of the
thickness of the flat crown portion is 1 mm or less. It is preferably 0.5 mm or less.
[0023] The tire frame member 12 is circular-shaped centered on the tire axis. Examples of
the resin material configuring the tire frame member 12 include thermoplastic resins
(including thermoplastic elastomers), thermoset resins, and other general-purpose
resins, and also engineering plastics (including super engineering plastics). These
resin materials do not include vulcanized rubber.
[0024] Thermoplastic resins (including thermoplastic elastomers) are polymer compounds of
materials that soften and flow with increasing temperature, and that adopt a relatively
hard and strong state when cooled. In the present specification, out of these, distinction
is made between polymer compounds of materials that soften and flow with increasing
temperature, that adopt a relatively hard and strong state on cooling, and that have
a rubber-like elasticity, considered to be thermoplastic elastomers, and polymer compounds
of materials that soften and flow with increasing temperature, that adopt a relatively
hard and strong state on cooling, and do not have a rubber-like elasticity, considered
to be non-elastomer thermoplastic resins.
[0025] Examples of thermoplastic resins (thermoplastic elastomers included) include thermoplastic
polyolefin-based elastomers (TPO), thermoplastic polystyrene-based elastomers (TPS),
thermoplastic polyamide-based elastomers (TPA), thermoplastic polyurethane-based elastomers
(TPU), thermoplastic polyester-based elastomers (TPC), and dynamically crosslinking-type
thermoplastic elastomers (TPV), as well as thermoplastic polyolefin-based resins,
thermoplastic polystyrene-based resins, thermoplastic polyamide-based resins, and
thermoplastic polyester-based resins.
[0026] As the thermoplastic materials described above, for example, materials may be employed
with a deflection temperature under load (at loading of 0.45 MPa), as defined by ISO
75-2 or ASTM D648, of 78°C or greater, a tensile yield strength, as defined by JIS
K7113, of 10 MPa or greater, a tensile elongation at break (JIS K7113), also as defined
by JIS K7113, of 50% or greater, and a Vicat softening temperature, as defined in
JIS K7206 (method A), of 130°C.
[0027] Thermoset resins are polymer compounds that cure to form a 3 dimensional mesh structure
with increasing temperature. Examples of thermoset resins include phenolic resins,
epoxy resins, melamine resins, and urea resins.
[0028] In addition to the thermoplastic resins (including thermoplastic elastomers) and
thermoset resins already listed above, general purpose resins may also be employed
as the resin material, such as (meth)acrylic-based resins, EVA resins, vinyl chloride
resins, fluororesins, and silicone-based resins.
[0029] Next, the reinforcing layer 14 is provided along the outer surface 22A of the flat
crown portion 22, and the end portions 14A at a tire axial direction outside of the
reinforcing layer 14 are positioned further to a tire axial direction inside than
a tire axial direction outside end portions of the flat crown portion 22. In other
words, the tire axial direction outside end portions 14A of the reinforcing layer
14 are positioned further to the tire axial direction inside than the center of curvature
O of the shoulder portions 20. The reinforcing layer 14 is configured by winding a
cord 30, which is covered with a cord covering layer 34 and formed using a resin material,
onto the outer surface 22A of the flat crown portion 22 along the tire circumferential
direction so as to form a spiral shape. The reinforcing layer 14 corresponds to a
belt layer disposed at the tire radial direction outside of a carcass ply in a conventional
rubber-made pneumatic tire. The tire axial direction outside indicates a direction
away from a tire equatorial plane CL, and the tire axial direction inside indicates
a direction approaching the tire equatorial plane CL.
[0030] The resin material employed in the cord covering layer 34 may be the same type of
resin material as that configuring the tire frame member 12, or may be a different
type. Employing, as the resin material, the same type of resin material to that configuring
the tire frame member 12, enables excellent bonding to be performed to the tire frame
member 12.
[0031] The outer surfaces of the bead portions 24 and the side portions 18 are covered by
a covering layer 28. A rubber may, for example, be employed as the covering layer
28.
[0032] As illustrated in Fig. 1 and Fig. 2, the tread 16 is provided at the tire radial
direction outside of the flat crown portion 22 and the reinforcing layer 14. The tread
16 is, for example, a pre-cured tread (PCT) formed using rubber. The tread 16 is formed
from a rubber having superior abrasion resistance to that of the resin material forming
the tire frame member 12. The same types of tread rubber as those employed in conventional
rubber-made pneumatic tires may be employed as the rubber, for example, styrene-butadiene
rubber (SBR). The tread 16 may be configured by employing another type of resin material
having superior abrasion resistance characteristics to the resin material forming
the tire frame member 12.
[0033] In tire axial direction cross-section, an outer surface of the tread 16 includes
a central region 16A, and end regions 16B. The central region 16A is provided at the
tire axial direction inside from the position (line E) of the end portions 14A of
the reinforcing layer 14, and is formed so as to be circular arc-shaped protruding
toward the tire radial direction outside. Origin points 16C of the end regions 16B
(boundaries between the central region 16A and the end regions 16B) are set so as
to be positioned between the position of the tire axial direction outside end portions
14A of the reinforcing layer 14, up to 2% of a tire axial direction width W of the
reinforcing layer 14 to the tire axial direction outside thereof. The width W of the
reinforcing layer 14 is a distance in the tire axial direction between end portions
of the cord covering layer 34. In the reinforcing layer 14, in cases in which the
cord 30 is not covered by the cord covering layer 34, the width W of the reinforcing
layer 14 is the distance in tire axial direction between the outside surfaces of the
cord 30 positioned furthest to the outside.
[0034] In tire axial direction cross-section, the end regions 16B at the outer surface of
the tread 16 are connected to the tire axial direction outside of the central region
16A, as illustrated in Fig. 2, and are formed further to the tire radial direction
inside than the extension line L of the central region 16A. For example, the end regions
16B are formed in tire axial direction cross-section so as to be circular arc-shaped
having a center of curvature P on the tire outside. The shape of the end regions 16B
is not limited thereto, and the end regions 16B where the reinforcing layer 14 is
not disposed may be any shape that is a shape capable of suppressing ground contact
under load.
[0035] As illustrated in Fig. 2, a cushion rubber 32 is disposed between the tread 16 and
the reinforcing layer 14, and between the tread 16 and the tire frame member 12, respectively.
The cushion rubber 32 is a non-vulcanized or semi-vulcanized rubber employed for bonding.
[0036] In Fig. 1, if TW denotes a width of the tread 16, and D denotes a fall amount of
a tire radial direction height difference between the outer surface of the tread 16
at the tire equatorial plane CL, and at the origin points 16C of the end regions 16B
(a boundary between the central region 16A and the end regions 16B), then D/TW = 0.03
to 0.05. Outside of this numerical range, it is difficult to achieve both a reduction
in rolling resistance and uneven wear resistance performance in the end regions 16B
of the tread 16. The outer surface means the tread face. The tire equatorial plane
CL is positioned in the central region 16A, and so the outer surface of the tread
16 at the tire equatorial plane CL means the tread face of the central region 16A.
Operation
[0037] Explanation follows regarding operation of the present exemplary embodiment, configured
as described above. In Fig. 1 and Fig. 2, in the tire 10 of the present exemplary
embodiment, the outer surface 22A of the flat crown portion 22 of the tire frame member
12 is formed so as to be flat along the tire axial direction. The reinforcing layer
14 is provided along the outer surface 22A of the flat crown portion 22, and the tire
axial direction outside end portions 14A of the reinforcing layer 14 are positioned
further to the tire axial direction inside than the tire axial direction outside end
portions of the flat crown portion 22.
[0038] This thereby enables deformation of the reinforcing layer 14 under load in the tire
axial direction to be suppressed more than in cases in which the end portions 14A
of the reinforcing layer 14 extends up to the vicinity of the shoulder portions 20
of the tire frame member 12. This thereby enables the rolling resistance to be reduced.
[0039] The end regions 16B at the outer surface of the tread 16 are positioned further to
the tire radial direction inside than the extension line L of the central region 16A,
enabling ground contact of the end regions 16B, where the reinforcing layer 14 is
not present in the layer below, to be suppressed. This thereby enables the uneven
wear resistance performance to be raised at the end regions 16B of the tread 16.
[0040] Moreover, the end regions 16B are formed so as to be circular arc-shaped with a center
of curvature P on the tire outside of the tread 16, thereby enabling ground contact
of the end regions 16B to be further suppressed. This thereby enables the uneven wear
resistance performance to be raised even more at the end regions 16B of the tread
16.
[0041] Due to the outer surface 22A of the flat crown portion 22 where the reinforcing layer
14 is disposed being flat, both rolling resistance and uneven wear resistance performance
can be achieved at the end regions 16B of the tread 16 by making D/TW from 0.03 to
0.05.
Explanation of the Reference Numerals
[0042]
- 10
- tire
- 12
- tire frame member
- 14
- reinforcing layer
- 14A
- end portion
- 16
- tread
- 16A
- central region
- 16B
- end region
- 16C
- origin point of end region (boundary between central region and end region)
- 18
- side portion
- 20
- shoulder portion
- 22
- flat crown portion
- 22A
- outer surface
- D
- fall amount
- L
- extension line
- P
- center of curvature
- TW
- width of central region
1. Reifen (10), umfassend:
ein Reifenrahmenglied (12), welches aus einem Harzmaterial besteht und Seitenabschnitte
(18) aufweist, welche an jeder Reifenaxialrichtungsseite angeordnet sind, Schulterabschnitte
(20), welche in der Reifenradialrichtung mit Außenendabschnitten der Seitenabschnitten
(18) verbunden sind, und welche so gekrümmt sind, dass sie in der Richtung der Außenseite
des Reifens in einem Querschnitt in der Reifenaxialrichtung vorstehen, und einen flachen
Kronenabschnitt (22), welcher mit den Schulterabschnitten (20) verbunden ist;
eine Verstärkungsschicht (14), welche entlang einer Außenfläche (22A) des flachen
Kronenabschnitts (22) bereitgestellt ist, und welche Außenendabschnitte (14A) in der
Reifenaxialrichtung aufweist, welche weiter in einer Reifenaxialrichtung zu Innenendabschnitten
hin angeordnet sind als zu Außenendabschnitten in einer Reifenaxialrichtung des flachen
Kronenabschnitts (22); und
eine Lauffläche (16), welche auf einer Außenseite in der Reifenradialrichtung außerhalb
des flachen Kronenabschnitts (22) und der Verstärkungsschicht (14) bereitgestellt
ist,
dadurch gekennzeichnet, dass
im Querschnitt in der Reifenaxialrichtung, eine Außenfläche der Lauffläche (16) einen
zentralen Bereich (16A) umfasst, welcher sich von einer Position der Außenendabschnitte
(14A) in der Reifenaxialrichtung der Verstärkungsschicht (14) zur Innenseite hin,
in der Reifenaxialrichtung erstreckt, um eine kreisförmige gebogene Form aufzuweisen,
welche zur Außenseite hin in der Reifenradialrichtung vorsteht, und Endbereiche (16B)
welche jeweils direkt mit einer Außenseite in der Reifenaxialrichtung des zentralen
Bereichs (16A) verbunden sind und zur Innenseite in der Reifenradialrichtung weiter
hin gebildet sind als eine Erstreckungslinie (L) des zentralen Bereichs (16A), und
wobei D/TW = 0,03 bis 0,05, wobei TW eine Breite der Lauffläche (16) ist, und D ein
Fallwert einer Höhendifferenz in der Reifenradialrichtung zwischen der Außenfläche
der Lauffläche (16) an einer Reifenäquatorialebene (CL) und an einer Begrenzung (16C),
zwischen dem zentralen Bereich (16A) und den Endbereichen (16B) ist.
2. Reifen nach Anspruch 1, wobei, im Querschnitt in der Reifenaxialrichtung, die Endbereiche
(16B) so geformt sind, dass sie eine kreisförmig gebogene Form aufweisen, dessen Krümmungsmittelpunkt
(P) auf einer Reifenaußenseite liegt.
1. Bandage pneumatique (10), comprenant :
un élément de cadre du bandage pneumatique (12) composé d'un matériau de résine et
comportant des parties latérales (18) positionnées au niveau de chaque côté dans la
direction axiale du bandage pneumatique, des parties d'épaulement (20) connectées
à des parties d'extrémité externes, dans la direction radiale du bandage pneumatique,
des parties latérales (18), et courbées de sorte à déborder vers un côté externe du
bandage pneumatique, dans une section transversale dans la direction axiale du bandage
pneumatique, et une partie de sommet plate (22) connectée aux parties d'épaulement
(20) ;
une couche de renforcement (14) agencée le long d'une surface externe (22A) de la
partie de sommet plate (22), et comportant des parties d'extrémité externes (14A),
dans la direction axiale du bandage pneumatique, qui sont positionnées davantage vers
des parties d'extrémité internes, dans une direction axiale du bandage pneumatique,
que vers des parties d'extrémité externes, dans la direction axiale du bandage pneumatique,
de la partie de sommet plate (22) ; et
une bande de roulement (16) agencée au niveau d'un côté externe, dans la direction
radiale du bandage pneumatique, de la partie de sommet plate (22) et de la couche
de renforcement (14) ;
caractérisé en ce que :
dans la section transversale dans la direction axiale du bandage pneumatique, une
surface externe de la bande de roulement (16) inclut une région centrale (16A) s'étendant
d'une position des parties d'extrémité externes (14A), dans la direction axiale de
la couche de renforcement (14), vers un côté interne, dans la direction axiale du
bandage pneumatique, de sorte à avoir une forme circulaire en arc, débordant vers
le côté externe, dans la direction radiale du bandage pneumatique, et des régions
d'extrémité (16B), connectées chacune directement à un côté externe, dans la direction
axiale du bandage pneumatique, de la région centrale (16A) et agencées davantage vers
l'intérieur, dans la direction radiale du bandage pneumatique, qu'une ligne d'extension
(L) de la région centrale (16A) ; et
dans lequel D/TW est compris entre 0,03 et 0,05, TW représentant une largeur de la
bande de roulement (16) et D représentant une quantité de réduction d'une différence
de hauteur, dans la direction radiale du bandage pneumatique, entre la surface externe
de la bande de roulement (16), au niveau du plan équatorial du bandage pneumatique
(CL), et une limite (16C) entre la région centrale (16A) et les régions d'extrémité
(16B).
2. Bandage pneumatique selon la revendication 1, dans lequel, dans la section transversale
dans la direction axiale du bandage pneumatique, les régions d'extrémité (16B) sont
formées de sorte à avoir une forme circulaire en arc, comportant un centre de courbure
(P) sur un côté externe du bandage pneumatique.